This Phase II application deals with non-invasive acoustic imaging of the oropharynx, hypopharynx, and larynx. Images of cross sectional area of the airway lumen as a function of axial distance along the airway are reconstructed from amplitudes and arrival times of acoustic returns measured at the airway opening. Although this imaging technology has been shown to be accurate, to require little or no subject cooperation, and to have important research applications, it has been too complicated to be used as a practical screening tool because it required the use of gas mixtures with high acoustic wavespeed, such as 20% 02-80% He. as a result of a fundamental acoustical constraint. In Phase I we established the feasibility of a new technical approach that circumvents that constraint, thereby simplifying the technology and allowing it to be employed using ordinary room air as the acoustic propagation medium. We established also in Phase I the feasibility of combining this technology with the simultaneous measurement of respiratory flows. Our aims for Phase II are. 1) to implement and refine the new technology and 2) to validate its utility as a screening tool. In Phase Il we focus this technology on two clinical circumstances that result in significant adverse outcomes with high prevalence: endotracheal intubation failure and obstructive sleep apnea. These circumstances were selected because the societal impact of the technology is expected to be immediate and because the associated commercial potential is thought to be large. PROPOSED COMMERCIAL APPLICATIONS Noninvasive imaging of extent and locus of airways obstruction. Established diagnostic applications include: reactive airways disease, asthma, disorders of airway growth, tracheal stenosis, obstructive sleep apnea. Potential diagnostic applications include indication for surgery and post- surgical evaluation in velopharyngeal incompetence. obstructive sleep apnea. vocal cord dysfunction. tracheal stenosis, tracheal reconstruction, preoperative assessment of difficult intubation.